Urinary tract infections (UTI) remain among the most common bacterial infections. They are a frequent cause of morbidity and constitute a large public health cost to society. Recurrent UTIs constitute a serious health problem, especially to adult women and female children. These infections are caused primarily by E. coli which infect the bladder by an ascending route from the fecal flora. Even in patients without demonstrable vesicoureteral reflux or obstruction, a lower tract UTI may proceed to pyelonephritis. The overall goal of this research is to establish a safe, effective vaccine treatment against UTI. The current approach to treating women with recurrent UTIs is to prevent infection by long-term administration of low dose antibiotics. This treatment is largely successful, but extended use of antibiotics carries the risk of allergic reactions in patients and development of antibiotic resistant uropathogens. An alternative treatment approach is to boost a patient's innate resistance to UTI by immunization. Two European research groups have tested parenteral and oral immunization against UTI with some success. We have previously demonstrated in animal models that vaginal mucosal immunization with killed bacteria can lessen the severity or duration of an induced UTI. Our current investigations are now focused on applying this immunization method in women susceptible to recurrent UTIs. During the past 2 years we have successfully completed a Phase I clinical trial which demonstrated no adverse effects from vaginal mucosal immunization. A Phase II clinical trial to test vaccine efficacy has been initiated in the past 6 months. Review of the early data indicates a positive treatment effect in immunized subjects. This ongoing research is the only U.S. clinical trial of a vaccine against UTI. In this proposal we will: 1) complete the Phase II clinical trial of vaginal mucosal immunization using a killed whole-cell vaccine, 2) identify E. coli antigens that are most responsible for eliciting UTI- protective antibodies, and 3) develop an acellular, endotoxin-free vaccine for stimulating protective antibodies in the urogenital tract.